joomla-build-sef-url.php

<?php
    
    function externalItem(Item $item)
    {
        if ($this->app->jbenv->isSite()) {
            return JRoute::_($this->app->route->item($item, false), false, 2);

        } else {
            $root        = JUri::root();
            $application = JApplicationCms::getInstance('site');
            $router      = $application->getRouter();
            $link        = $router->build($this->app->route->item($item, false));

            return $root . preg_replace('/^.*administrator\//', '', $link, 1);
        }
    }